A year ago, the Rockefeller Brothers Fund announced that it would be divesting from fossil fuels, news that garnered huge attention for the obvious reason that the Rockefeller fortune was made in the oil industry. The announcement also came with an implicit challenge: If RBF could dump its fossil fuel stocks, why couldn't any other foundation follow suit—especially with more evidence piling up that climate change poses a threat to everything foundations care about?

Looking into our crystal ball at Inside Philanthropy, we predicted that it wouldn't be long before the divestment train started to really move fast, generating panic among foundations that weren't hopping on board—particularly high-profile funders like Hewlett that work on climate change.

As we wrote at the time, after the RBF move: "Glaring contradictions tend to be hard for major institutions to sustain, especially when people start paying attention." The Hewlett and Packard foundations are not only top climate funders, they love to boast about their green headquarters—even as they refuse to renounce investing in companies that ferociously fight action on climate change and sell a product that threatens civilization as we know it. What's wrong with that picture?

We went on:

It may take a while before the fossil fuel divestment dominoes are truly falling fast, but once they are, little will stop the trend. And with RBF's move, the pace just picked up in a big way.

At some point, as the dynamic changes, the question for a place like Hewlett becomes this: Do you want to earn kudos for being on the vanguard? Or do you want to take fire for lagging behind, and just end up in the same place anyway?

But it's hard to say exactly when the dominoes might start falling. When you’re dealing with billions of dollars in endowments and long-established investing strategies, things tend to move slowly. Right now, the list of foundations that have pledged to avoid fossil fuel investments remains modest.

Still, one thing we know about changes within the philanthropic sector is that they are often strongly influenced by broader societal trends. Foundations may be accountable to no one, but they don't like finding themselves out of step with the times or falling behind other key institutions. And when they move, they often move in herds—sometimes in a stampede.

Which is why a recent report showing rising momentum around the movement to divest from fossil fuels is so important. The study, conducted by Arabella Advisors and commissioned by DivestInvest, found that:

The divestment movement has grown exponentially since Climate Week in September 2014, when Arabella Advisors last reported that 181 institutions and 656 individuals representing over $50 billion in assets had committed to divest.

In the past year more than a hundred and fifteen philanthropic organizations with assets totaling more than $10 billion have committed to divest their portfolios of fossil fuels.

To date, 436 institutions and 2,040 individuals across 43 countries and representing $2.6 trillion in assets have committed to divest from fossil fuel companies.

You read that right: The assets being steered away from fossil fuels have grown from $50 billion to $2.6 trillion in just the past year.

According to the press release announcing the report, global financial institutions HSBC, Citigroup, Mercer and the Bank of England all agree that portfolios exposed to fossil fuel assets are at a significant quantifiable risk. And one sure-fire way to get people to pay attention is to mess with their money. Thomas Van Dyck, managing director and financial advisor of SRI Wealth Management Group, put things this way:

More and more investors are reducing their carbon risk today and diversifying their portfolios with the goal to harness the upside in the sustainable clean growth industries of the future. That underscores what I see every day as a financial advisor–that the demand for fossil-free investment products is increasing.

RBF's Stephen Heintz also made the economic argument last year. “John D. Rockefeller, the founder of Standard Oil, moved America out of whale oil and into petroleum,” said Heintz. “We are quite convinced that if he were alive today, as an astute businessman looking out to the future, he would be moving out of fossil fuels and investing in clean, renewable energy.”

Okay, so there's not only a moral case for dumping fossil fuel stocks, but a growing business case, too.

To us, the handwriting seems so clearly on the wall that most big foundations will, eventually, feel compelled to divest from fossil fuels. One possible scenario is that foundations will find themselves increasingly isolated as other top nonprofits—most notably major universities—shed their fossil fuel investments. In contrast to foundations, other nonprofits have major constituencies that can force change—we're already seeing students and alumni ratchet up divestment pressure on campuses. Falling dominoes among these cousin institutions will put more heat on foundations to divest.

But really: Why should foundations be dragged kicking and screaming to a decision that is the right thing to do? Foundations are supposed to be the institutions that can take risks and operate on the cutting edge. They're supposed to be leaders, not followers. Places like Hewlett, Packard, and MacArthur have certainly done that with their grantmaking on climate. Now they need to do the same with their endowments.

And if they're not sold on divestment by the moral or economic arguments, they might heed this wise advice: "If you know where you're going to end up, try to get there gracefully."